I received this in email today. I haven't even begun to digest it all yet, but it really gives one a sense of the many complexities that must be considered by those who would compete in a game like this. It's kind of long, but I thought some of you would like to see it.

It's also kind of exciting to get a glimpse of the things planned for MSL. Now, I better appreciate some of the stuff the various space mission teams had to consider before they were selected for the end game. This is interesting stuff...

Oh, and just in case anyone thinks I am one of the "colleages" it was addressed to, I'm not. I just managed to land in some address list.

You are invited to participate in the First Landing Site Workshop for the 2009 Mars Science Laboratory (MSL) rover mission to Mars. The workshop will be held May 31 through June 2, 2006, in Pasadena, California.

AN OVERVIEW OF WORKSHOP OBJECTIVES:

The purpose of the Landing Site workshop is to identify and evaluate potential landing sites best suited to achieving stated mission science objectives within the constraints imposed by engineering requirements, planetary protection requirements, and the necessity of ensuring a safe landing. A NASA-appointed Landing Site Steering Committee and the Mars Science Laboratory Project will use the results of the workshop as the basis for narrowing the list of potential landing sites under consideration. Community consensus with respect to high priority sites will also be solicited. In addition, the workshop will provide a means for identifying potential landing sites as targets for imaging by the MGS, Odyssey, MRO, and perhaps other orbital assets. Note: the number of potential landing sites is high because MSL entry, descent, and landing capabilities enable a small landing error ellipse (20 km diameter), high landing site altitude (<2 km), and wide latitudes (±60°).

MISSION SCIENCE OBJECTIVES:

The primary scientific goal of the Mars Science Laboratory (MSL) is to assess the present and past habitability of the martian environments accessed by the mission. Habitability is defined as the potential of an environment to support life, as we know it. Such assessments require integration of a wide variety of chemical, physical, and geological observations. In particular, MSL will assess the biological potential of the regions accessed, characterize their geology and geochemistry at all appropriate spatial scales, investigate planetary processes that influence habitability, including the role of water, and characterize the broad spectrum of surface radiation. To enable these investigations, MSL will carry a diverse payload capable of making environmental measurements, remotely sensing the landscape around the rover, performing in situ analyses of rocks and soils, and acquiring, processing, and ingesting samples of rocks and soils into onboard laboratory instruments. A candidate landing site should contain evidence suggestive of a past or present habitable environment. To the extent that it can be determined with existing data, the geological, chemical, and/or biological evidence for habitability should be expected to be preserved for, accessible to, and interpretable by the MSL investigations.

The MSL project has been assigned to Category IVc by NASA's Planetary Protection Office with constraints on the landing site and regions accessed from it. Specifically, MSL is limited to landing sites not known to have extant water or water-ice within one meter of the surface. Later access to "special regions" defined in NPR 8020.12C (regions where terrestrial organisms are likely to propagate, or interpreted to have a high potential for the existence of extant martian life forms) is permitted only in the vertical direction through use of sterilized sampling hardware. The above are general guidelines for site selection; compliance of specific landing sites and nearby regions will be determined through discussions with the Planetary Protection Office during the site selection process.

MISSION ENGINEERING CONSTRAINTS:

Because the ability to ensure a successful landing for MSL is paramount, consideration of landing sites must include comprehensive assessment of limitations imposed by mission engineering constraints. Although these constraints continue to be established and refined, a description of preliminary values related to allowable locations, elevation, and surface properties follows.

The entry, descent and landing scenario employed by the Mars Science Laboratory (MSL) flight system places engineering constraints on what would be considered a safe landing site of high scientific interest. The dominant considerations in landing site placement are latitude, elevation and the landing ellipse size. The MSL flight system is capable of landing in a circle of 20 km diameter, within which everywhere must be safe for landing and roving. This circle can be placed anywhere on Mars that is below +2 km MOLA elevation and within 60° latitude of the equator (60°N to 60°S). Steady state horizontal and vertical winds and wind gusts are a concern during descent and landing, so areas with potentially high winds will need to be compared with landing system tolerance during development. The landing system uses a radar altimeter, so the entire landing site must be radar reflective. Slopes at long and intermediate (2-5 km and 20 m) wavelength could negatively impact the altimeter, requiring slopes over 2-5 km length scales <3° and slopes over 20 m length scales <15°. Short wavelength slopes affect landing stability and trafficability, requiring slopes over 5 m length scales <15°. Rocks higher than 0.6 m are a problem for landing, requiring areas with intermediate or lower rock abundance. The landing surface must be load bearing and trafficable and so must not be dominated by dust. Persistent cold surface temperatures and CO2 frost will negatively impact performance. These latter three considerations will likely eliminate areas with very low thermal inertia and very high albedo. Surface characteristics (short wavelength slope, rocks and dust) of a trafficable surface are similar to those required for safe landing, except the small landing ellipse and long traverse capability allow the possibility of considering "go to" sites. These sites have a safe landing site adjacent to the target of science interest and require traversing outside of the landing ellipse to sample the materials of highest interest. In this case, the area that must be traversed to get into the region of highest science interest (required to accomplish the science objectives of the mission) must be trafficable from anywhere within the ellipse. All of the values for the parameters discussed will be refined during continuing design and development of the spacecraft, with updates posted on the web site, as will a more detailed discussion of these constraints. We expect the first posting around February 1, 2006 at http://marsoweb.nas.nasa.gov/landingsites/ and the USGS PIGWAD site: http://webgis.wr.usgs.gov/msl

All persons planning to participate in the workshop should review the science, engineering, and planetary protection constraints carefully, as only those landing sites that meet these constraints will be accepted for presentation at the workshop.

HOW TO PARTICIPATE:

All members of the scientific community are encouraged to participate in this important activity. Persons wishing to make a presentation at the workshop are urged to carefully review the science objectives and engineering and planetary protection constraints at http://marsoweb.nas.nasa.gov/landingsites/ and at the USGS PIGWAD web site noted above.

Most of the workshop will be devoted to submitted papers describing: (1) the overall types of sites for MSL based on associated scientific and programmatic rationale and suitability for safe landing and roving; and (2) individual landing sites on Mars and their scientific merit and safety. Individuals must prepare an abstract (no longer than one page using standard LPSC abstract format) summarizing their proposed topic or site. Talks advocating an individual site must summarize the science merits and demonstrate that the proposed location satisfies the mission science, planetary protection, and engineering requirements. A clear statement of the rationale for continued consideration as a possible landing site should also be included. A program will be prepared from the submitted abstracts and will be posted along with logistical information in late April, 2006.

Abstracts (no longer than one page using standard LPSC abstract format) are due by March 28, 2006, and should be submitted electronically via http://marsoweb.nas.nasa.gov/landingsites/. Detailed instructions on abstract format and submission will also be posted at this web site in February, 2006.

LOGISTICS FOR THE WORKSHOP:

The workshop will be held in the vicinity of JPL in Pasadena, CA, and there will not be a registration fee. In order to get a sense of the number of people likely to attend the workshop, interested individuals should indicate their intent to attend via http://marsoweb.nas.nasa.gov/landingsites/ by April 1st, 2006. Although we anticipate mostly oral presentations, there may also be poster sessions. Additional logistical information about the workshop will be distributed to the community in subsequent announcements and will be posted at: http://marsoweb.nas.nasa.gov/landingsites/ and http://webgis.wr.usgs.gov/msl Input from the science community is critical to identification of optimal landing sites for the MSL. We look forward to your involvement in these activities!

Back in June 2002, the MSL science steering group wanted MSL to have substantial onboard autonomy allowing it to drive between its locations for detailed sampling and study at the rate of fully 450 meters/sol, or 3 km in 13 sols -- and, once it arrived, to "be able to approach a designated target, deploy the instrument arm, mini-corer, or drill, and begin science activities (measurements or drilling/coring), using only a single command cycle to initiate the full suite of activity." ( http://trs-new.jpl.nasa.gov/dspace/bitstre...4/1/02-1822.pdf ) . A typical plan based on this idea involved it, during 667 sols of operation, driving about 69 km to study 23 different detailed study locations for about 16.5 sols each.

"(1) PSlG wanted to balance science and engineering sophistication: Mission life driven much less by driving range, speed or hazard detection autonomy than by number of science decisions requiring human interaction at a rock sample site.

"(2) Large vehicle size allows for simple path planning.

"(3) Consistent with an 'autonomy to cost' strategy: Hazard detection and avoidance test cost could be unbounded. Could infuse more autonomy once science objectives are met."______________________________

Assuming, again, that MSL spent a total of about 381 sols at its detailed study locations, it could drive only about 1/9 as far as in the earlier plan -- that is, about 7.7 km. And the new plan called for it to acquire 74 samples, each of which would now take about 7 sols to approach and collect -- so we're talking only about 150 sols worth of driving at 50 meters/sol, which again came out to only about 7.5 km.

Well. Now we're back up to an ability to traverse 100-150 meters/sol during long drives, so -- assuming that we still plan to spend about 380 sols collecting samples -- we are indeed back up to 15 to 22.5 km total drive distance.

...they went back to the MER level of driving and target-approach autonomy... a 3-sol cycle to approach any particular sampling target at one of its detailed study locations.

As I recall, Steve Squyres' retrospective wish list for the MERs includes six-wheel steering that would avoid repeated, time consuming back and forth jogs to reposition in front of a target or obstacle. Any chance of the MSL having six-wheel steering? Or is the thought of having six steering actuators subject to failure too scary?

As I recall, Steve Squyres' retrospective wish list for the MERs includes six-wheel steering that would avoid repeated, time consuming back and forth jogs to reposition in front of a target or obstacle. Any chance of the MSL having six-wheel steering? Or is the thought of having six steering actuators subject to failure too scary?

Instead of adding two steering actuators it seems to make more sense to me to simply remove the two non-steering middle wheels. In other words, make it a single rocker-bogie suspension instead of a double. Make the (4) wheels a bit bigger and you end up with what Steve wanted at less weight and better equipped for crossing ripples. If you place the wheels far apart, it doesn't cost you much stability either.

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